This invention relates to a roller dampening assembly for an offset printing press. It relates more particularly to an assembly of this type which can easily be moved away from its contacting plate cylinder to an accessible location to permit quick plate change-over for successive jobs and servicing of the plate cylinder and other ancillary press parts and to facilitate maintenance of the dampening assembly.
Offset presses require a dampening assembly to moisten the surface of the press plate cylinder. There are many different types of dampening systems used on offset printing presses. A typical dampening assembly includes a rotating water fountain roller which picks up water from a fountain pan and transfers it as a film to an adjacent contacting metering roller which, in turn, applies a water film of the desired thickness to an ink and water roller. That roller also receives ink from a contacting ink roller and transfers ink and water films to the print cylinder. The water adheres to the "no print" areas of the print cylinder while the ink which is hydrophobic adheres to the "print" areas thereof. The printed matter on the cylinder is thereupon transferred to a blanket cylinder which contacts the web to be printed. Of course, there are other types of dampeners using ductors which apply moisture to plate cylinder rather than to an ink and water roller.
In a vertical press, the paper moves vertically and printing cylinders and rollers are located on both sides of the web path. This configuration results in the dampener assembly blocking access to the plate cylinder. Thus, for plate change-over to run different jobs, the operator is required to go under the plate cylinder and dampener assembly. This makes the plate change-over time-consuming and inefficient.
In order to allow access for plate change-over, the dampening assembly has heretofore been mounted on rollers permitting it to be rolled out laterally from the press. Such roll-out dampening assemblies tend to be relatively expensive. Also space must be available to accommodate the rolled out assembly. Finally those prior assemblies have various components which are prone to wear. This not only increases maintenance down time but also creates tolerance problems which make it more difficult to properly position the dampening assembly at its operative location in the press.